This invention relates to fastener assemblies, and particularly to fastener assemblies for mounting wheels.
Two-piece wheel fastener assemblies consisting of a nut/bolt and a pressure ring have previously been employed for fastening wheels. For example, a two-piece nut with pressure ring assembly is described in Goiny U.S. Pat. No. 4,969,788. Drawbacks inherent in such two-piece designs include inconsistent torque tensions, and rotation of the conical pressure ring within the wheel surface wherein it is seated (cf., Col. 4, II. 9-12 of Goiny patent). Rotation of this pressure ring, combined with the softness of wheel materials and high compressive stresses, can result in galling or welding of the nut/bolt to the wheel.
Hlinsky U.S. Pat. No. 4,362,449 discloses a wheel fastener with a fastener body, a pressure washer rotatably mounted on the fastener body, and a plastic washer therebetween. This plastic washer has the disadvantage of a low hardness that allows the plastic washer to deform plastically when the fastener is tightened in place. Such plastic deformation can result in a relaxation of the clamping force applied by the tightened fastener, which is undesirable in most applications.
The present invention is directed to overcoming these and other disadvantages inherent in prior-art systems.
The scope of the present invention is defined solely by the appended claims, and is not affected to any degree by the statements within this summary.
Briefly stated, a wheel fastener assembly embodying features of the present invention comprises a fastening member, a frustoconical metal thrust washer, and a pressure ring having an undersurface which is oriented to contact a depression in a workpiece.